3) On the Output tab select Unknown USB Device, or if your headset device is listed (like Logitech headset) select it. Set the balance to center and output volume about 3/4 of the way up, Mute is NOT checked.

8) Make sure the Voice tab is selected and set the controls to the following:

Check the first three checkboxes (Enable Outgoing, Use Push-To-Talk, Play Key Clicks)
Set your HotKey to Command (just for testing)
Silence Time should be setting at 3 (and not changeable)
Sensitivity to 60
Ignore the Codec and format popups
Set Sound Output and Input Devices to Unknown USB Device
Set Line Input slider to Max
Set Outbound to 4 (Max)
Set Inbound to 10 (Max)

9) Click ok.

10) Click the Setup Button again (the settings you set above should still be there)

11) Click the Test Button

12) Press and release the Command key (you should hear a tone in the headset indicating the button was pressed and then when it was released)
In the Scroll Box in the middle of the Setup Window, it should say
-- Begin --
-- End --

13) Press the Command key again and speak a few words, then release the command key. As before the scrollbox should now say
-- Begin --
-- End --
-- Begin --
-- End --
and you should hear yourself played back through the headset

14) Click the Test button again to finish testing and click OK.

If all of the above steps went smoothly, your vent is set up and properly configured. Your issue is either incorrect server information, or some issue outside of Ventrilo. Please see this thread for troubleshooting.